This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This collaboration with Dr. Mehmet Toner of the BioMEMS Center at Harvard University (a P41 Resource) is focused on applying microfabrication techniques to the development of a high-throughput large particle sorter in R&D Project 2. We are investigating passive particle manipulation within microfluidic channels. Using a variety of specific channel orientations, the BioMEMS Center has been able to show particle focusing, periodic particle spacing, and parallel streamlines with no external fields. We are investigating the use of this technology to focus particles in the 100-micron diameter range. We expect this approach to easily scale to this dimension and fabrication of multiple focusing channels on a single substrate should be straight- forward. As such we have obtained a few sample chips and analyzed focused particles in a simple fluorescence analysis device, with some success. The advantages of this approach include robustness, reproducible operation and no need for any external particle manipulation field.